A gas turbine includes, in serial flow order, a compressor, a combustion section and a turbine. In particular configurations, the gas turbine includes an inlet system positioned upstream from an inlet to the compressor. The inlet system generally includes various filters, cooling coils, moisture separators, and/or other devices which may be used to purify and otherwise condition air or other working fluid entering the gas turbine. In particular configurations, the filters may be self-cleaning.
Gas turbine systems often include an air processing unit (APU) that provides an air supply for pulsing compressed air across and/or through the self-cleaning filters, thus blowing debris and/or contamination away from the filters. In addition, the APU may provide an air supply to one or more valves as instrument air. The air supplied to the APU is typically extracted directly from the compressor. For example, the air may be extracted from an extraction port disposed at a particular stage of the compressor and/or from a discharge casing that is downstream from the compressor.
The air extracted from the compressor is relatively hot (i.e. 400-800° F.) and requires substantial cooling and lowering of pressure prior to injection into the filter housing. Various devices such as air-to-air heat exchangers and pressure reduction valves are provided within the APU to cool and reduce pressure of the air supply upstream from the inlet and/or instrumentation. However, in warm climates, the air-to-air heat exchangers may struggle to provide sufficient cooling to the air upstream from the inlet system. Accordingly, an improved air supply and conditioning system for a gas turbine system would be useful.